This invention relates to a cannula or sheath and particularly to a cannula usable with angiographic catheters.
In certain angiographic studies, the angiographer uses the Desilets-Hoffman procedure to do a multiple study. In this procedure, the angiographer obtains access to a patient's blood vessel by inserting a hollow needle through the skin and into the lumen of the blood vessel. A guidewire is passed through the needle and advanced through the artery or vein into the organ to be studied. The needle is removed leaving the guidewire in the organ. A cannula and dilator are advanced over the wire into the vessel and the dilator is removed along the guidewire. The angiographer can then conduct the multiple studies by inserting various types of catheters into the vessel through the cannula or sheath.
In order to avoid excessive bleeding and to insure against the possibility of an air embolism, this technique requires occlusion of the passage through the cannula during catheter changes. When such occluding is performed manually there is always the possibility that it will not be accomplished as quickly as desired and will not be continuously effective for as long as desired. In one type of prior art hemostasis cannula, represented by the Stevens U.S. Pat. No. 4,000,739, a cannula valve is provided that is only intended to prevent blood loss from the vessel.
However, it is also desirable that the cannula valve be effective in preventing air flow into the blood vessel. The patent to Timmermans, U.S. Pat. No. 4,430,081, shows a cannula valve adapted to be effective in preventing both blood loss from and air flow into the blood vessel. The Timmermans cannula valve employs a first, second and third disk-like gasket mounted in the cannula passage. The patent to Suzuki, et al., U.S. Pat. No. 4,610,674, shows a catheter introducing instrument in which the introducer valve includes a single flexible disk having a pair of intersecting incisions formed from the top and bottom surfaces of the disk. However, the Suzuki introducer valve generally is not adapted to permit easy introduction and manipulation of larger diameter catheters.